عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ أَمَرَنِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ أَنْ أَبِيعَ غُلَامَيْنِ أَخَوَيْنِ فَبِعْتُهُمَا فَفَرَّقْتُ بَيْنَهُمَا فَذَكَرْتُ ذَلِكَ لِلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فَقَالَ أَدْرِكْهُمَا فَأَرْجِعْهُمَا وَلَا تَبِعْهُمَا إِلَّا جَمِيعًا
It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him), he says: The Messenger of Allah (peace and blessings be upon him) ordered me to sell two slaves; they were brothers to each other. I sold them, but I separated them from each other, and then I informed the Messenger of Allah (peace and blessings be upon him) of this. He (peace and blessings be upon him) said: Find both of them and return them, and do not sell them except together.